In recent years, lithium ion batteries with high output and high energy density have drawn attention as consumer electric device power sources such as mobile phones. Further, the application of such lithium ion batteries to driving power sources such as ships, railroads, and automobiles has been desired. A lithium ion battery includes a positive electrode and a negative electrode which can occlude/discharge lithium ions and a separator in a container. The positive electrode and the negative electrode include a metal plate such as an aluminum foil or a copper foil, a positive electrode active material, and a negative electrode active material. As the positive electrode active material, a lithium cobalt oxide (LiCoO2) having a laminar rock salt structure, powder made of an oxide of lithium and a transition metal where a part or all of cobalt atoms of the lithium cobalt oxide is replaced with nickel or manganese or the like is used, for example. Carbon or the like has been used for the negative electrode active material.